1. Field of the Invention
The present invention relates to data entry devices for entering graphical data into data processing or communication systems and, more particularly, to pad devices for the direct entry of such data by a user.
2. Description of the Prior Art
It is well known in the prior art to construct graphical data entry devices in which a user may depress a point on a grid area to enter a point of graphical data into a communication system. Examples of such devices are shown in U.S. Pat. No. 2,900,446, No. 3,304,612, No. 3,699,439, and No. 3,806,912. Another example is disclosed in U.S. Pat. No. 3,522,663 in which a flexible member coated with a conductive layer is positioned above a base member which is coated with a resistive material so that the location of a point at which the two members are pressed together can be determined by measuring the resistances from the edges of the layer of resistive material to that point.